
console.log( undefined == null ); // true
console.log( undefined === null ); // false

console.log( typeof 'kaifamiao' ); // string

// 原始类型	<-------->	包装对象
// string	<-------->	String
// number	<-------->	Number
// boolean	<-------->	Boolean
// bigint	<-------->	BigInt
// symbol	<-------->	Symbol


console.log( `100` === '100' );


let sum = 0 ;
for ( let i = 1 ; i <= 100 ; i++ ){
	if ( i % 2 == 0 ) {
		sum = sum + i;
	}
}
console.log( sum );


let x = 100 , y = 200 ;
while( x++ < --y );
console.log( x , y );


let a = 100 , b = 200 ;
let c = a++ + --a + --b + b-- ;
console.log( a , b );


let array = [ 56 , 28 , 93 , 46 , 75 ] ;
console.log( array.length );
array.push(88);
console.log( array.length );

console.log( array );
array[1] = 99 ;
console.log( array );


console.log( typeof ( '1024' + 0 ) );
console.log( '1024' / 0 , typeof ( '1024' / 0 ) );
console.log( '1024' * 1 , typeof ( '1024' * 1 ) );
console.log( '1024' / 1 , typeof ( '1024' / 1 ) );



console.log( 100 / 'kaifamiao' );